Antibodies to the Group B meningococcal (identical to the Escherichial coli K1) capsular polysaccharide are not conveniently measured with existing technologies. The reason for this inability to measure antibodies to the protective antigens of these two bacterial species is not well understood. The antigen, an Alpha2-8 linked N-acetyl neuraminic acid polymer is an unusual bacterial capsular polysaccharide because it does not elicit antibodies when injected into adult humans, it is susceptible to mammalian enzymes and its structure closely resembles sialic acid components of gangliosides especially those present in high concentration during fetal development. The group B meningococcal polysaccharide has been covalently bound to a carrier protein and has been shown to elicit antibodies with protective activities in laboratory animals. Monoclonal antibodies, derived from hybridoma cultures, exclusively the IgM class have been produced and characterized. Methods for producing oligosaccharides of varying length have been devised in order to find out which oligomer most effectively inhibits the homologous reaction between antimonclonal antibodies or an antiserum taken from horse extensively immunized with Group B meningococcal organism strain B11.